About this specific stone:
This one is a smaller stone i got from a good french friend in exchange with another stone. It looks yellow-green (YG) tending to move into yellow. It has some well visible plant inclusions. Slurrying the stone is very easy, its a soft stone, so probably thats why the “French Thuringian” name was created,

General Information on La Pierre Du Sud Ouest or the french Mystery StoneThese Stones often appeared in certain areas of france but also as buys from UK. They have often been used in older paddle sized hones.

After searching a while in end March 2015 i came over a gallery from an Italien Museum (The Museum of Natural History of the Academy of Fisiocritici) where they showed different types of stones. One of those stones had a comparable appearance like the stones which have been showed on the French and US Shaving boards. Not only the appearance was a factor, but the interesting thing was that it was mentioned to have been explicitly used as a Razor Hone.

Is the Mystery over now ?
I don’t know because there was no possibility to prove this trail on any evidence. Actually in a certain time somebody might show up with some local examples and might to a crosscheck with the stones from members of the shaving boards. Until this didn’t happen, this trail will be a foggy one.

History on the Pierre Sud-Ouest :Members from the french Coupechouxclub forum mentioned that these stones have mostly been found in the south-east region of france and sometimes in spain. Actually they had Italian and spanish guest workers to a certain time in these regions where the stones have been found on fleamarkets, so this could be a possible explanation about the appearance of these stones in France in certain areas.